This invention relates to a pneumatic radial tire free from the occurrence of a step wear which tends to occur at the end portions of the shoulders of a tire.
Examples of the measures for preventing the step wear which have been taken in the past include the provision of subgrooves on the shoulder ribs and the provision of a number of cuts or kerfs on the shoulder edges. The provision of subgrooves on the shoulder ribs of a tire is effective for prevention of the occurrence of step wear. However, this expedient causes a remarkable lowering in the rigidity of the shoulder ribs, which in turn leads to a lowering in the cornering power and driving stability. On the other hand, the provision of a number of cuts or kerfs on the shoulder edges brings about not only the occurrence of cracking or cupping at the end of the cuts or the end of the kerfs but also a lowering in the driving stability due to the lowering in the rigidity of the shoulder ribs. Further, this expedient has an additional problem of an increase in the mold cost etc.